Technologies for a wireless charger are as follows. Usually, a direct current is converted into a high frequency AC, and then a high frequency AC electrically drives an emission coil to transfer alternating electric magnetism to a receiving coil and then converts the sensed alternating current into the direct current and transmits the direct current to devices as power supply, as shown in patent literatures CN200510030239.4 and CN201110020352.X.
A wireless charging emitter product usually includes four parts, namely a DC power supply module, a DC power transmission line, a wireless charging transmission circuit module and an transmission coil module, wherein the DC power supply module usually is an adapter and a large-capacitance battery, and the DC power transmission line is a conventional power wire only suitable for transmission of power DC electricity and low-frequency signal AC electricity, for example a USB wire. The wireless charging transmission circuit module and the transmission coil module usually are installed in the same housing, and merely installed in two or more housings which are partly and closely connected in a mechanical way to form a group, thus facilitating production and installation, meeting the demands on the frame design of the existing wireless charging emitter, and being practically operable. For example, patent CN201220552440.4 discloses the realization mode the majority of the existing wireless charging emitter product. Some wireless charging emitter products have the DC power module, the wireless charging transmission circuit module and the transmission coil module assembled in one housing, and do not have the DC power transmission line, as shown in CN201220725129.5.
The wireless charging transmission circuit module has an efficiency usually lower than 90% during DC-AC conversion, and therefore causes certain power loss and generates a lot of heat. The power loss is usually not smaller than 1 W and the heat is equivalent to the heat generated by two small bulbs. During the actual wireless charging process, the housing transmits a great amount of heat to the wireless charging receiving devices, so the heat received by the receiving device is more than the heat generated when the charging is directly executed by using a lead. Thus, the service life of the product and the reliability of the product are affected, and at the same time, many potential users dare not to use the wireless charger and worry about dangers such as the receiving devices exploded because of being too hot.
To solve the above problems, during the design of the exiting wireless charging emitter product, the transfer and dissipation of the heat must be taken into consideration to reduce the heat transmitted to the receiving devices as much as possible. However, the cost in housing design and materials during the manufacturing are increased first. According to the thermodynamic principle, the existing wireless emitter cannot realize small size, ultra-thinness, and extremely low heating temperature at the same time. Therefore, the thickness of the existing wireless charging emitter cannot be lower than 5 mm, and the interior capacitance of the housing cannot be smaller than 32,000 mm3(bigger than a cigarette case). At the same time, during wireless charging, the temperature rise of the receiving device is higher than 25° C. (maximum rise over 40° C.), so many wireless charging emitters are manufactured by using technologies such as “increasing heat dissipating holes, using heat-dissipating silica gel in a large area, designing uneven housing surface to increase heat dissipation.” However, the effect is undesirable effect; cost is increased; product appearance is not good; and most important is that a large space is occupied, affecting the daily use of users.
For example, use of the wireless chargers on a dining table, tea table, and desk is the mostly desired effect of the developers of such products, so users can charge devices at any time and at any place. Meanwhile, economical benefits are increased, while social life is promoted. However, in actual use, due to the thickness and size of the existing wireless chargers, and due to limit in the use of the wireless charging emitter product in areas within the reach of user's arms, it is very easily for users to “move, press and turn” the wireless charging emitter in daily life, hindering user and causing damage. At the same time, the wireless chargers also affect other aspects of the daily life, for example, “a large area is occupied, and there is no more space for may tee cup, or my eraser is invisible when the wireless charging is not needed.” Therefore, the wireless charger can get into daily life only by reduction of the size and thickness of the wireless charger. However, the prior art fails to do so.
For example, various tables manufactured in a furniture plant can be added with the wireless emitter products. If the existing wireless charger is used, a large hole must be bored on the table top to embed the wireless charger, as shown in the patent CN201320440252.7. Meanwhile, installation and decoration are executed by using expensive technologies. Finally, the cost of every table with the wireless charging emitter function is several times that of a common table. Therefore, such product has no marketing value. Moreover, boring a hole on a table is impossible in many cases. There is no suitable solution for neglecting the thickness or size of the wireless charger. Therefore, the wireless chargers using such technology cannot be promoted in a large area and has no significance for social development.
Practical and potential sales volume determines the production cost and the price. Large-scale promotion of the wireless charger products is impossible in current situations, and the wireless charger products are accepted by some fans in a very small scope. This is why the existing wireless charger product is 10 and even more times expensive than the traditional wired charger and cannot be quickly widely popularized.